Air supply systems are utilized especially for supplying air spring damper units for the leveling control of a motor vehicle within a closed loop but also to supply external consumers.
U.S. Pat. No. 6,726,189 discloses one such air supply system in various embodiments.
In the first embodiment of FIG. 1 of this patent, the air supply system comprises: several air spring damper units arranged in parallel to each other, a compressor and a pressurized air store. A 2/2-directional valve is assigned to each air spring damper unit and the air spring damper units are connected via a common ring line to the intake end as well as to the pressure end of the compressor. In this ring line, a switchable intake valve is also provided. A second ring line connects the pressurized air store to the intake end and to the pressure end of the compressor. In this ring line, an air dryer is arranged on the pressure end which has a free flow via a throttle check valve in the through-flow direction to fill the pressurized air store and this through-flow is throttled in the opposite through-flow direction for flushing the air dryer.
In this air supply system, the compressor can transfer pressurized air from the air spring damper units into the pressurized air store and, in the opposite direction, fill the air spring damper units with air from the pressurized air store. Furthermore, the compressor can supply the air spring damper units or the pressurized air store with fresh air from the atmosphere. A further function comprises venting pressurized air into the atmosphere from the pressurized air store in the opposite direction via the air dryer in order to regenerate the latter. Several directional valve units are provided in both ring lines to realize these various functions. Accordingly, and in accordance with FIG. 1, two parallelly-connected 2/2-directional valves are used for the first ring line and two likewise parallelly-connected 2/2-directional valves are used for the second ring line.
This embodiment of the air supply system has the disadvantage that no consumer, which lies outside of the closed loop, can be supplied with pressurized air. In this way, the power capacity of the compressor is not fully utilized.
Accordingly, in FIG. 8 of U.S. Pat. No. 6,726,189, a second embodiment provides for a branching between the compressor and the air dryer for a line connection to supply an external consumer. With this embodiment of the air supply system, for example, a tire-fill apparatus can be operated as shown.
This embodiment has the disadvantage that it is very complex and therefore very expensive with respect to its manufacture. This is caused by the additional units for tire filling and has its cause, however, also in the plurality of 2/2-directional valves required for the closed loop.